Many schemes have been developed for emitting free electrons into space, or a vacuum. The classic, and very early, electron emitter includes a cathode and a heater positioned adjacent to the cathode for heating the cathode sufficiently to cause electrons to be emitted. Typical examples of this type of electron emission can be seen in cathode ray tubes (CRTs) and all of the vacuum tubes previously used in electronic equipment. This structure and process is unwieldy because it requires a large amount of power to heat the cathode. Also, the heat from the heater has a tendency to cause damage in other adjacent components so that other components must be spaced from the structure. Further, an additional power supply, other than the one supplying the flow of electrons, is generally required for the heater. This adds additional cost as well as the space required.
Other apparatus for emitting electrons include devices called field emission devices (FEDs) which generally require relatively large voltages to cause the electrons to be emitted from a sharp tip of metal. In some applications the sharp tip is coated with a material. Such as cesium or diamond, to reduce the potential barrier at the surface of the emitter. In some of these devices the voltages required are reduced somewhat.
In yet another apparatus and method for emitting free electrons into space the photoelectron phenomenon is utilized. In this method and/or apparatus, electrons in a material that is bombarded with photons gain sufficient energy to thereby overcome a potential barrier of the emitting material. This procedure does not produce convenient apparatus since it is difficult to sufficiently raise the density of the photons.
Devices for emitting electrons into space are used in displays of all types, and can be used to replace vacuum tubes and/or transistors and the like in certain applications. It is, therefore, desirable to provide electron emitters which are convenient to use, require low voltages and operate at approximately room temperature.
It is a purpose of the present invention to provide a new and improved electron emitter.
It is a further purpose of the present invention to provide a new and improved electron emitter which operates on relatively low potentials.
It is another purpose of the present invention to provide a new and improved electron emitter which operates at room temperatures.
It is still another purpose of the present invention to provide a new and improved electron emitter which is not extremely bulky or difficult to manufacture and which, therefore, is less expensive in terms of space and fabrication techniques.